1. Field of the Invention
The present invention relates to golf balls. More particularly, the present invention relates to improvement of dimples of golf balls.
2. Description of the Related Art
Golf balls have numerous dimples on the surface thereof. The dimples disrupt the air flow around the golf ball during flight to cause turbulent flow separation. By causing the turbulent flow separation, separating points of the air from the golf ball shift backwards leading to the reduction of drag. The turbulent flow separation prolongs the gap between the separating point on the upper side and the separating point on the lower side of the golf ball, which results from the backspin, thereby the lift force that acts upon the golf ball is enhanced. Reduction in drag and elevation of lift force are referred to as “dimple effect”. Excellent dimples disturb the air flow more efficiently. Owing to the excellent dimples, great flight distance can be achieved.
It is known to persons skilled in the art that a great dimple effect is achieved according to golf balls having the dimples densely arranged. Some proposals have been made in connection with dimple pattern aiming at improvement of the dimple effect.
JP-A-S50-8630 (U.S. Pat. Nos. 4,729,861, 4,936,587 and 5,080,367) discloses a golf ball provided with numerous dimples having a uniform size. In this golf ball, pitch is smaller than 0.065 inch for most of the dimple pairs. According to this golf ball, relationship between the pitch and dimple diameter was not considered. In comparison with general dimple diameter, the pitch of 0.065 inch is not small enough. According to the pattern of the dimples having a uniform size, the diameter can not be set to be great. The dimples in this golf ball are not arranged densely enough.
JP-A-S62-192181 (U.S. Pat. No. 4,813,677) discloses a golf ball provided with large dimples and small dimples. In this golf ball, high dimple density is achieved by arranging small dimples in the region surrounded by multiple large dimples. However, the small dimples are not sufficiently responsible for the dimple effect.
JP-A-H4-347177 (U.S. Pat. No. 5,292,132) discloses a golf ball having the dimples arranged so that any rectangle having a predetermined size can not be formed on the land. In this golf ball, small proportion of the land is achieved by arranging many small dimples. However, the small dimples are not sufficiently responsible for the dimple effect.
Top concern to golf players for golf balls is their flight distance. In light of flight performance, there is room for improvement of the dimple pattern. An object of the present invention is to provide a golf ball that is excellent in the flight performance.